U.S. patent application number 11/464912 was filed with the patent office on 2007-03-01 for device authentication using a unidirectional protocol.
Invention is credited to Michael L. Davis, Tam Hulusi.
Application Number | 20070046424 11/464912 |
Document ID | / |
Family ID | 37561170 |
Filed Date | 2007-03-01 |
United States Patent
Application |
20070046424 |
Kind Code |
A1 |
Davis; Michael L. ; et
al. |
March 1, 2007 |
DEVICE AUTHENTICATION USING A UNIDIRECTIONAL PROTOCOL
Abstract
The present invention is directed toward secure access systems.
Specifically, a method and system is provided that allows a control
panel of a secure access system to verify the authenticity and
fidelity of a reader within the secure access system by utilizing a
rolling code agreed upon by the reader and the control panel.
Inventors: |
Davis; Michael L.; (Amhert,
NY) ; Hulusi; Tam; (Irvine, CA) |
Correspondence
Address: |
SHERIDAN ROSS PC
1560 BROADWAY
SUITE 1200
DENVER
CO
80202
US
|
Family ID: |
37561170 |
Appl. No.: |
11/464912 |
Filed: |
August 16, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60713528 |
Aug 31, 2005 |
|
|
|
Current U.S.
Class: |
340/5.8 ;
340/572.1 |
Current CPC
Class: |
G07C 9/28 20200101; G07C
9/27 20200101; H04L 63/1466 20130101; H04L 63/126 20130101 |
Class at
Publication: |
340/005.8 ;
340/572.1 |
International
Class: |
G05B 19/00 20060101
G05B019/00; G08B 13/14 20060101 G08B013/14 |
Claims
1. A method of maintaining a secure access system that uses a
unidirectional communication protocol, the secure access system
comprising at least one credential, at least one reader, and a
device upstream of said reader, comprising: reading a credential
with a reader; said reader generating a first message comprising
credential data associated with said credential and a first code;
transmitting said first message to an upstream device; and said
upstream device, analyzing said credential data in order to
determine the authenticity of said credential and further analyzing
said first code in order to determine the authenticity of said
reader.
2. The method of claim 1, further comprising: said reader
generating a second message comprising a second code, wherein said
second code is different from said first code; transmitting said
second message to an upstream device; and said upstream device
analyzing said second code in order to determine the authenticity
of said reader.
3. The method of claim 2, wherein said second message is generated
a predetermined amount of time after said first message is
generated.
4. The method of claim 2, wherein said second message is generated
in response to receiving a prompting signal from said upstream
device.
5. The method of claim 1, wherein said first message is encrypted
by said reader prior to transmitting said first message to said
upstream device and decrypted by said upstream device prior to
analyzing said first message.
6. The method of claim 1, wherein a code selection algorithm is
used to generate said first code.
7. The method of claim 6, wherein said code selection algorithm
generates said first code based upon at least one of time of day,
total operation time of said reader, a reader unique ID, number of
cards read, and a reader manufacturer ID.
8. The method of claim 6, wherein said code selection algorithm
generates said first code based upon a number of messages
previously transmitted from said reader to said upstream
device.
9. The method of claim 1, wherein said first code is a unique code
chosen from a rolling code list.
10. The method of claim 9, further comprising: said upstream device
accessing a second list that corresponds to said rolling code list;
said upstream device comparing said first code to one or more valid
codes from said second list; determining that said first code
matches a valid code; and in response to said upstream device
determining that said first code matches said valid code, said
upstream device determining that the authenticity of said reader is
valid.
11. The method of claim 1, wherein said transmitting utilizes a
Wiegand protocol.
12. The method of claim 1, wherein said credential is machine
readable and comprises at least one of an RFID device, a contact
smart card, a contactless smart card, a proximity card, a magnetic
stripe card, a barium ferrite card, a bar code, a Wiegand card, a
PDA, and a cellular phone.
13. The method of claim 1, wherein credential data is at least one
of a user name, a social security number, a title, access
permissions, a key, a password, a manufacturer ID, site code,
customer code, and a unique ID.
14. The method of claim 1, wherein said upstream device is at least
one of a control panel, a host computer, a processor, a database,
and an intermediate device.
15. The method of claim 1, wherein said reader comprises a second
device that generates the codes.
16. The method of claim 15, wherein said second device is integral
with a housing of said reader.
17. A method of maintaining a secure access system that uses a
unidirectional communication protocol, comprising: providing a
downstream device associated with at least one interrogator device
that is operable to transmit a rolling code as a part of a message;
providing an upstream device that is operable to receive said
message and analyze said rolling code; requiring said downstream
device to transmit a first message comprising a first valid rolling
code at a first time; and requiring said downstream device to
transmit a second message comprising a second valid rolling code at
a second time.
18. The method of claim 17, wherein at least one of said first and
second is a window of time in which said downstream device is
required to transmit said message.
19. The method of claim 17, wherein at least one of said first and
second message is time stamped in order to verify to said upstream
device that said at least one of said first and second message was
transmitted at their respective required time.
20. The method of claim 17, further comprising, determining a
required first and second time of check in.
21. The method of claim 20, wherein at least one of said first and
second time is before at least one of said required first and
second time of check in.
22. The method of claim 20, wherein at least one of said first and
second time related is after at least one of said required first
and second time of check in.
23. The method of claim 17, wherein in response to said downstream
device not transmitting at least one of said first and second valid
rolling codes, determining that said downstream device is at least
one of fraudulent and malfunctioning.
24. The method of claim 17, wherein in response to said downstream
device not transmitting said first rolling code, determining that
said downstream device is at least one of fraudulent and
malfunctioning.
25. The method of claim 24, wherein in response to determining that
said downstream device is at least one of fraudulent and
malfunctioning, performing an invalid reader logic action.
26. The method of claim 25, wherein said invalid reader logic
action is at least one of sounding an alarm, notifying
security/maintenance personnel that said downstream device is
defective, not opening a door, and disabling said downstream
device.
27. A secure access system utilizing a unidirectional communication
protocol, comprising: a credential; a reader that is operable to
read credential data from said credential upon presentation of said
credential to said reader, generate a message comprising some or
all of said credential data and code data, and to transmit said
message; an upstream device that is operable to receive said
message and upon receiving said message is operable to analyze said
credential data in order to determine the authenticity of said
credential and to analyze said code data in order to determine the
authenticity of said reader.
28. The system of claim 27, wherein said message is encrypted by
said reader prior to transmitting said message to said upstream
device and decrypted by said upstream device prior to analyzing
said message.
29. The system of claim 28, wherein a key is used to encrypt and
decrypt said message.
30. The system of claim 27, wherein the code is a rolling code.
31. The system of claim 30, wherein a code selection algorithm is
used to generate said rolling code.
32. The system of claim 31, wherein said code selection algorithm
generates said rolling code based upon at least one of time of day,
total operation time of said reader, a reader unique ID, and a
reader manufacturer ID.
33. The system of claim 31, wherein said code selection algorithm
generates said first code based upon the number of messages
previously transmitted from said reader to said upstream
device.
34. The system of claim 30, wherein said rolling code is a unique
code chosen from a rolling code list.
35. The system of claim 34, wherein said upstream device is further
operable to access a list corresponding to said rolling code list,
compare said rolling code to a valid code from said list, determine
that said first code matches said valid code, and in response to
determining that said first code matches said valid code, determine
that the authenticity of said reader is valid.
36. The system of claim 27, wherein said message is transmitted by
said reader utilizing a Wiegand protocol.
37. The system of claim 27, wherein said credential is at least one
of an RFID device, magnetic stripe card, bar code, barium ferrite
card, and smart card.
38. The system of claim 27, wherein said upstream device is an
intermediate device.
39. The system of claim 27, wherein said upstream device is a
control panel.
40. A device adapted for use in a secure access system utilizing a
unidirectional communication protocol, comprising: an input adapted
to receive messages from a reader, wherein at least a portion of
said messages comprise a code; an authentication member operable to
determine the authenticity of said reader based upon an analysis of
said code; and an output operable to transmit said message to an
upstream device, wherein said message is transmitted to said
upstream device in response to said authentication member
determining the authenticity of said reader is valid.
41. The device of claim 40, wherein at least a portion of said
messages are encrypted prior to being received at said input, and
wherein said authentication member is operable to decrypt said
message prior to said analysis of said code.
42. The device of claim 40, wherein said authentication member is
further operable to encrypt said message after said analysis of
said code and prior to being transmitted at said output.
43. The device of claim 40, wherein said authentication member
comprises a valid rolling code sequence and wherein said valid
rolling code sequence is used by said authentication member to
analyze said code.
44. The device of claim 40, wherein said authentication member
transmits a prompting signal to said reader that prompts said
reader to generate a message comprising a code.
45. The device of claim 40, wherein said message further comprises
credential data that is related to a credential and wherein said
authentication member is further operable to determine the
authenticity of said credential based on said credential data.
46. A device for use in a secure access system that uses a
unidirectional communication protocol, wherein said device is
operable to read credential data from a credential, comprising: a
code generator that is operable to generate a first message
comprising credential data associated with a credential that is
used to determine the authenticity of said credential and a first
code that is used to determine the authenticity of said device; and
an output for transmitting said first message to an upstream
device.
47. The device of claim 46, wherein said code generator is further
operable to generate a second message comprising a second code,
wherein said second code is different from said first code.
48. The device of claim 47, wherein said second message is
generated a predetermined amount of time after said first message
is generated.
49. The device of claim 47, wherein said second message is
generated in response to receiving a prompting signal from said
upstream device.
50. The device of claim 46, wherein said first message is encrypted
by said code generator prior to transmitting said first message to
said upstream device.
51. The device of claim 46, wherein said code generator comprises a
code selection algorithm.
52. The device of claim 51, wherein said code selection algorithm
generates said first code based upon at least one of time of day,
total time of operation, a reader unique ID, and a reader
manufacturer ID.
53. The device of claim 51, wherein said code selection algorithm
generates said first code based upon a number of messages
previously transmitted from said device to said upstream
device.
54. The device of claim 51, wherein said code selection algorithm
changes in response to receiving a prompting signal from said
upstream device.
55. The device of claim 46, wherein said code generator comprises a
rolling code list.
56. The device of claim 55, wherein said code generator changes how
the rolling code list is used in response to receiving a prompting
signal from said upstream device.
57. The device of claim 56, wherein said prompting signal is
transmitted randomly from said upstream device.
58. The device of claim 46, wherein said upstream device comprises
a reader and wherein a credential comprises said code generator.
Description
[0001] This application claims benefit of U.S. Provisional Patent
Application Ser. No. 60/713,528, filed Aug. 31, 2005, which is
herein incorporated by this reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention is generally directed to
authentication of a reader in a secure access system. More
specifically, the present invention provides a reader signal
protocol used to protect and differentiate authorized, authentic
readers from non-authorized, non-authentic readers in a secure
access system.
BACKGROUND
[0003] Limiting or securing access to designated or sensitive areas
is an important issue. As such, there is a current focus on
technological systems for controlling access to designated areas in
both the private and public venues. Such systems must be made
highly impervious to attack by those wishing to gain unauthorized
access to the secured area.
[0004] In access control systems, Radio Frequency Identification
Devices (RFIDs) or other security credentials are typically used to
store data that uniquely identify a holder of the RFID device or
the holder's access authorizations. In order to gain access to an
asset, such as a building, room, safe, computer, files,
information, etc., a holder presents the RFID device to a reader
that reads the data and subsequently transmits the data to a panel,
processor, or a host system where a decision is made to either
grant access to the subject asset or not. There are also readers
that combine the functionality of a panel/host and the physical
reader into a single unit that makes the access decision. This type
of device is sometimes referred to as a stand-alone reader.
[0005] Attention has been focused on the security mechanisms
employed by RFID cards to protect and secure the data exchange
between the RFID device and the reader. Some of these techniques
include the use of cryptography, mutual key authentication, secure
channels, and even protection of the chip on the RFID device
against physical and electrical attacks. However, little attention
has been given to ensuring the integrity of the communications
between the reader and its host/control panel as well as insuring
the integrity of the reader itself.
[0006] A working assumption thus far has been that RFID device
readers are trustworthy devices, when in fact this may not be the
case. In many building access control applications, a reader is
mounted on the unsecured side of a door in a location that is not
under continuous scrutiny. In such a case, compromise of a single
reader could result in a compromise of RFID device security if any
secret information, such as keys, authorization codes and the like,
were somehow extracted from the reader.
[0007] In addition, without knowing the authenticity of the reader
an unauthorized or rogue reader could be used to replace an
existing legitimate reader in a security system. This rogue reader
can actually be any reader or data reply device capable of
outputting data in the same format as the replaced reader.
[0008] In the access control industry, one of the most popular
communication protocols used between a reader and a panel is the
Wiegand protocol. Due to its popularity, the Wiegand protocol has
become a de-facto industry standard. It is estimated that the
majority of today's access control panels support the Wiegand
protocol as the primary method to connect readers to the panel. It
should be noted that several companies use their own proprietary
communications protocols, but they still support the Wiegand
protocol due to its popularity and widespread use. Because of this,
a variety of non-RFID machine readable ID readers and other devices
have standardized on the Wiegand protocol. Examples of these
readers support smart card, proximity, magnetic stripe, bar code,
barium ferrite, etc. There are also keypads, biometric devices,
wireless Wiegand protocol extenders, protocol converters, and even
robots that utilize the Wiegand protocol. The Security Industry
Association (SIA) also recognizes the Wiegand protocol as an
important standard in the access control industry. The Wiegand
protocol has become so important that it has been published as an
industry standard.
[0009] The Wiegand protocol is essentially a unidirectional
protocol that only provides for data transmission from a reader to
an upstream device (e.g., a control panel, host, or processor).
Although there is a signal sent back from the upstream device to
the reader, this signal is essentially a logic signal used to
convey status to a cardholder by controlling a reader's LED. A
superset of the Wiegand protocol adds additional logic signals to
control an audible device in the reader and provides for additional
reader LED colors. These are not bi-directional protocols because
substantive data is still sent in only one direction. The host
cannot give the reader a command. Only simple signals are sent from
the host to the reader.
[0010] As popular as the Wiegand protocol has become, it has
shortcomings. Examples of these shortcomings include the fact that
the Wiegand protocol is susceptible to electrical noise, has
distance limitations, and only allows data to be sent from a reader
to an upstream device. Without bidirectional capabilities, it is
very difficult to implement a modern protocol that provides for
reader authentication.
[0011] Another issues is that the Wiegand protocol allows "party
line" connections so that it is very easy to connect one or more
additional devices to communication wires to monitor the
communications between a card reader and a host in an attempt to
harvest data streams to be used to compromise the system. Once a
rogue device has been connected to monitor communications between
the reader and control panel, an attacker could merely note when
the door has been unlocked and flag the most recent data stream as
one that will open the door. Then, whenever illicit entry is
desired, the attacker could just "replay" that data stream causing
the door to unlock. The attacker need not even remove the device
from the communication wires because the Wiegand communications
utilize an "open collector" electrical interface, which allows both
the monitoring of messages and generation of messages from that
same connection.
[0012] There is typically little stopping an attacker from
harvesting one or more valid messages to gain illicit entry using
different cardholder's data so that no suspicions are aroused.
Accessibility to the Wiegand communications wires is increased by
the fact that a reader is typically located on the unsecured side
of a wall or door and, because of the nature of access control, may
be at a location that is not under continuous observation or
scrutiny. Making matters worse, many access control readers do not
employ a tamper mechanism so that the removal of a reader to access
the internal wiring or even to replace the reader with another
compromised reader or illicit Wiegand generating device is
undetectable.
[0013] There have been some attempts to address the shortcomings of
the Wiegand protocol. One example of an extension to the Wiegand
protocol is described in U.S. Pat. No. 6,988,203 to Davis et al.,
the contents of which are hereby incorporated herein by this
reference. The '203 patent describes appending additional bits to
the Wiegand data stream. This provides supplementary information
from the reader to the upstream device as well as a CRC or other
type of error detection and/or correction bits covering all of the
data in the transmission. The '203 patent further describes
transmitting data back to the reader from the upstream device via
an LED control line.
[0014] Additionally, in PCT Application No. WO 2005/038729 to
Merkert, which is herein incorporated by this reference, an access
system that includes a signal generator located between a reader
and a control panel is described. The reader utilizes a dynamic
timing element that ensures a replay attack cannot be used to gain
unauthorized access to an asset. The reader stamps any signal sent
therefrom with a time stamp indicating when the message was
generated. Then the control panel reads the time stamp to ensure
that the message is authentic. An attempt to harvest a signal and
resubmit that signal again at a later time will result in the
control panel determining the signal is invalid. To ensure channel
security between system elements, encryption and/or digital
signatures are used. unfortunately, this solution does not overcome
most of the Wiegand deficiencies.
[0015] For instance, there is no way in the currently existing
solutions that allows the control panel to continually monitor each
reader in order to verify the fidelity of each reader. Thus,
leaving open the possibility of having a valid reader replaced with
a rogue reader without the system or system operator becoming aware
of such actions.
SUMMARY
[0016] The present invention is generally directed toward a method,
apparatus, and system that allows for authentication of readers in
a secure access system. Although well suited for use in an access
system utilizing the Wiegand protocol, embodiments of the present
invention may be suitable for use in any system utilizing a
unidirectional protocol.
[0017] In accordance with embodiments of the present invention, a
method of checking authenticity of devices in a secure access
system utilizing a unidirectional communication protocol is
provided. The method comprises the steps of reading a credential
with a reader, the reader generating a first message that includes
credential data associated with the credential and a first code,
transmitting the first message to an upstream device, and the
upstream device analyzing the credential data in order to determine
the authenticity of the credential and further analyzing the first
code in order to determine the authenticity of the reader.
[0018] A valid reader employing the above-described method will be
able to verify its authenticity to the upstream device by sending a
valid code. A reader that is not enabled to generate a valid code
may be identified by the upstream device as defective and/or
fraudulent. By requiring the reader to send a valid code along with
credential data, the upstream device can be confident that the
reader is valid and has not been tampered with.
[0019] In accordance with further embodiments of the present
invention, a method of maintaining a secure access system that
utilizes a unidirectional communication protocol is provided. The
method comprises the steps of providing a downstream device that is
operable to transmit a valid rolling code as a part of a message
and further providing an upstream device that is operable to
receive the message and analyze the rolling code. The method can
continue by determining a required first time of check in and
requiring the downstream device to transmit a first message
including a first valid rolling code at a first time related to the
required time of check in. The method may then determine a required
second time of check in that is after the required first time of
check in, and require the downstream device to transmit a second
message including a second valid rolling code at a second time
related to the required second time of check in.
[0020] By requiring a downstream device to check in with the
upstream device at a particular time schedule, the upstream device
can continually update the state of the system. In other words, the
upstream device can determine fairly quickly, depending on the
amount of time between required check in times, whether a
downstream device has been tampered with, replaced, and/or is
malfunctioning. If the time between required check in messages is
very short, like one second or less, it becomes very difficult for
an attacker to perform any action that would interrupt
communications between the upstream device and the downstream
device.
[0021] In one embodiment of the present invention, certain
thresholds may be set at the upstream device that allows for missed
messages due to noise or the like. For example, a threshold of N
missed messages may be allowed for a particular downstream device.
Thus, if a downstream device misses one predetermined check in
time, it is not necessarily identified as malfunctioning or having
been tampered with. Rather, the downstream device is allowed to
miss up to N check-ins, which may or may not be consecutive, before
an error determination is made.
[0022] In accordance with other embodiments of the present
invention, a secure access system utilizing a unidirectional
communication protocol is provided. The system comprises a
credential, a reader that is operable to read credential data from
the credential upon presentation of the credential to the reader,
generate a message including the credential data and rolling code
data, and to transmit the message, and an upstream device that is
operable to receive the message and upon receiving the message is
operable to analyze the credential data in order to determine the
authenticity of the credential and to analyze the rolling code data
in order to determine the authenticity of the reader.
[0023] In accordance with still further embodiments of the present
invention a device adapted for use in a secure access system
utilizing a unidirectional communication protocol is provided. The
device comprises an input that is adapted to receive a message from
a reader, where the message includes a rolling code, an
authentication member operable to determine the authenticity of the
reader based upon an analysis of the rolling code, and an output
operable to transmit the message to an upstream device in response
to the authentication member determining the authenticity of the
reader is valid.
[0024] The device may be an intermediate device that is used only
to monitor the authenticity of readers in a given system. The
intermediate device may also be adapted to analyze credential data
received from the reader in order to make a determination about the
authenticity of a credential that was presented to the reader. The
intermediate device may be employed in order to ensure that
communications between a rogue reader and a control panel do not
occur, thus protecting the control panel from potentially harmful
signals. This provides a provision for updating legacy systems with
embodiments of the present invention without requiring the
replacement of a reader or host.
[0025] These and other advantages will be apparent from the
disclosure of the invention(s) contained herein. The
above-described embodiments and configurations are neither complete
nor exhaustive. As will be appreciated, other embodiments of the
invention are possible using, alone or in combination, one or more
of the features set forth above or described in detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a diagram depicting an exemplary system for
authenticating credentials with legitimate readers in accordance
with embodiments of the present invention;
[0027] FIG. 2 is a block diagram depicting an exemplary reader and
control panel utilizing a unidirectional data transfer protocol in
accordance with embodiments of the present invention;
[0028] FIG. 3 is a flow chart depicting a method of generating a
message for transmission to an upstream device in accordance with
embodiments of the present invention;
[0029] FIG. 4 is a flow chart depicting a method of receiving and
processing a message at an upstream device in accordance with
embodiments of the present invention;
[0030] FIG. 5 is a flow chart depicting a method of transmitting a
message in order to verify authenticity of downstream device to an
upstream device in accordance with embodiments of the present
invention;
[0031] FIG. 6 is a flow chart depicting logic within an exemplary
upstream device in order to verify the authenticity of downstream
devices in a secure access system in accordance with embodiments of
the present invention; and
[0032] FIG. 7 is a block diagram depicting a data structure that
can be used by both the upstream and downstream device in order to
maintain a secure access system in accordance with embodiments of
the present invention.
DETAILED DESCRIPTION
[0033] The present invention is generally directed toward a reader
authentication method, device, and system. The invention
advantageously addresses deficiencies of the prior art and may be
utilized within the context of access control or security systems,
as well as be equally efficiently utilized in a broad range of
other applications using a unidirectional communications protocol
where interactive computerized data acquisition techniques are
used, both contactless or requiring a physical contact with a
carrier of pre-programmed information (e.g., monitoring moving
objects, tracking inventory, verifying credit cards, and the
like).
[0034] FIG. 1 depicts an access network 100 used to verify the
identity of at least one credential. In one embodiment of the
present invention, the system 100 comprises a control panel 104, a
hub 108, a plurality of readers 1121-n, and a plurality of
credentials 1161-m such that n and m are integers wherein
n.gtoreq.1, m.gtoreq.1, and typically m is greater than n. The
plurality of readers 1121-n may include readers 112 of the same
type, as well as readers of different types. For example, a subset
of the plurality of readers 1121-n may be legacy readers (e.g.
readers using older transmission protocols). Whereas another subset
of the plurality of readers 1121-n may be new readers utilizing
more secure protocols including the protocols described herein.
[0035] Additionally, the system 100 may further comprise
intermediate devices 120 connected between a reader 112 and the
control panel 104. In the depicted embodiment, the readers 112 are
coupled to an intermediate device 112 through interface 132. The
intermediate devices 120 are coupled to the hub 108 through
interface 128 and the hub is coupled to the control panel 104 via
interfaces 124. In an alternate embodiment (not shown), the readers
112 may be coupled to the respective inputs/outputs of the control
panel 104 without a device, like the hub 108 or intermediate device
120, existing there between. Interfaces 124, 128, and 132 between
the readers 112, the intermediate devices 120, the hub 108, and the
control panel 104 are generally unidirectional interfaces, which
may selectively be implemented in a form of wired, wireless,
fiber-optic communication links, or combinations thereof.
[0036] As can be appreciated by one of skill in the art, the
interfaces 124, 128, and 132 may be implemented utilizing buses or
other types of connections. For example, the I/O ports may be one
or more of a USB port, parallel port, serial port, Small Computer
Systems Interface (SCSI) port, modem, Ethernet, and/or an RF
interface. The protocols used to communicate between the control
panel 104 and the readers 112 may include one or more of the TCP/IP
protocol, RS 232, RS 485, Current Loop, Power of Ethernet (POE),
Bluetooth, ZigBee, GSM, WiFi, and other communication methods and
protocols known in the art.
[0037] An exemplary intermediate device 120 comprises an input that
is adapted to receive signals via interface 132, an output that is
adapted to transmit signals via interface 128, and an
authentication member 140. The authentication member 140 is
operable to determine the authenticity of one or more readers 112
associated with the intermediate device 120 (e.g., determine
whether the reader 112 is valid or not), based upon a rolling code
that is transmitted from the reader 112 to the intermediate device
120.
[0038] The control panel 104 may be a general-purpose computer
adapted for multi-task data processing and suitable for use in a
various settings (e.g. commercial, industrial, residential, and the
like). A memory of the control panel 104 comprises software
program(s) containing a database of records for the system 100.
Alternatively, a database 144 may be separated from the control
panel 104. The database 144 whether integral to the control panel
104, separate from the control panel 104, or both, maintains
records associated with the readers 112, credentials 116 and their
respective holders or users, algorithm(s) for acquiring, decoding,
verifying, and modifying data contained in the readers 112,
algorithm(s) for testing authenticity and validity of the
credentials 116, and algorithm(s) for implementing actions based on
the results of these tests. The database 144 may further comprise a
list of valid rolling codes and their corresponding required time
of check in and/or algorithm(s) for generating valid rolling codes
and comparing them with rolling codes received from a downstream
device.
[0039] As used herein, in reference to an individual or an object
associated with a credential 116, the terms a "holder" and a "user"
are used interchangeably.
[0040] Each reader 112 is adapted for exchanging information with
the control panel 104 and for requesting data from the credential
116 placed in the active zone of the reader. The reader 112 may
also be adapted for processing at least a portion of the data
acquired from the credential 116. Alternatively, processing of the
acquired data may be performed using the control panel 104
exclusively. In one embodiment, the reader 112 generates signals
facilitating execution of the results of interrogating the
credential 116 (e.g., engages/disengages a locking mechanism,
allows/disallows movement of a monitored article, temporarily
disables itself, activates an alarm system, updates a database, and
the like). Alternatively, the control panel 104 may generate such
signals.
[0041] In accordance with embodiments of the present invention, a
stand-alone reader 112 may be utilized to perform the functionality
of both the reader 112 and the control panel 104. This stand-alone
reader may include, or have access to, the database that contains
data used to determine the authenticity of a credential and/or
algorithm(s) used to make the determination of authenticity of the
credential 116. A determination of authenticity for a credential is
made at the receiving point rather than having to transmit data
across a network from the reader to a control panel 104 in order to
make a determination of authenticity. The stand-alone reader is
further operable to execute instructions based upon the analysis of
the credential 116.
[0042] Specific configurations of the control panel 104 are
determined based on and compliant with computing and interfacing
capabilities of the readers 112 and/or the hub 108.
[0043] At least a portion of the plurality of readers 112 further
comprise a code generator 148. The code generator 148 is used by
the reader 112 to generate a code, possibly a rolling code, in
order to verify its authenticity to an upstream device. The code
generator 148 may comprise a table, sequence, or data structure of
valid rolling codes that the reader 112 can work through as update
signals are generated. The code generator 148 may also comprise a
code generating algorithm that creates a valid code based on
certain criteria.
[0044] Interface 136 represents the communication interface that
exists between a reader 112 and a credential 116. Interface 128 may
represent an RF communication interface, a biometric communication
interface, a keypad, a magnetic communication interface, an optical
communication interface, or combinations thereof.
[0045] In operation a credential 116, for example a credential, is
brought into an active zone of the reader 112 in order to establish
the communication interface 136. For a credential, a Radio
Frequency (RF) communication interface 136 between the reader 112
and the credential is typically automatically established when the
credential is brought within an active zone of a
reader/interrogator 112. The active zone of an RF reader 112 is
defined as a three dimensional space where the intensity of RF
signals emitted by the reader 112 exceeds a threshold of
sensitivity of the credential and the intensity of RF signals
emitted by the credential exceeds a threshold of sensitivity of the
reader 112. When a credential is presented to most readers, such a
communication interface 136 is established and the reader 112 and
credential begin transmitting data back and forth.
[0046] The credential 116 may also be implemented in a number of
other machine readable devices including, but not being limited to,
contact smart card, a contactless smart card, a proximity card, a
magnetic stripe card, a barium ferrite card, a bar code, a Wiegand
card, a PDA, a cellular phone and any other type of device used to
store and transmit data relating a particular application. The
active zone for each type of credential 116 may vary based upon the
type of communications used between the reader 112 and the
credential 116. For example, a magnetic stripe card is placed in
the active zone of the reader 112 when it is swiped through the
reader 112. As can be appreciated by one of skill in the art, the
interface 128 is created upon presentation of the credential 116 to
the reader 112 such that communications between the two is
facilitated.
[0047] The reader 112 takes the information that it retrieves from
the credential 116 and generates a signal to send to the control
panel 104. In generating the signal the reader 112 creates a
credential part of the signal and a rolling code part of the
signal. The code generator 148 is typically operable to generate
the code part of the signal. The credential data relates to the
credential that was read (e.g., user name, social security number,
title, access permissions, key, password, manufacturer ID, site
code, customer code, unique ID, etc.) The code data or rolling code
data is a number, letter, dataset, and/or identifier chosen from
possibly a list of potential rolling codes. The rolling code sent
from a valid reader 112 may possibly be a code previously agreed
upon by the control panel 104 and reader 112. The reader 112 and
control panel 104 may cycle through and agree upon a number of
valid rolling codes as time progresses in order to provide a more
secure system.
[0048] Once the control panel 104 receives the signal from the
reader 112, the control panel 104 will analyze the credential data
from the signal to determine if the credential 116 is authorized to
gain access to the asset associated with the reader 112.
Additionally, the control panel 104 will analyze the rolling code
portion of the signal to determine if the reader 112 is authorized
to send commands and has not been tampered with. In an alternative
configuration, the signal is sent from the reader 112 to the
intermediate device 120 where the rolling code data is analyzed by
the authentication member 140 in order to determine if the reader
112 is still valid and has not been tampered with. The intermediate
device 120 then forwards the signal on to the control panel 104 for
verification of the credential 116. In still a further
configuration, the reader 112 generates a signal containing only
the credential data and forwards that signal on to the intermediate
device 120. The intermediate device 120 then generates rolling code
data and incorporates that into the signal from the reader 112. The
intermediate device 120 then forwards the signal on to the control
panel 104 for verification of the credential and rolling code data.
As can be appreciated, any upstream device within the system 100
may perform the verification of the credential data and/or the
rolling code data generated by a downstream device. However, it is
advantageous to have the reader 112 verified by a device that
resides in a secured area rather than an unsecured area so that the
device verifying the authenticity of the reader 112 may not be as
easily compromised.
[0049] Referring now to FIG. 2 a typical Wiegand protocol reader
112 and control panel 104 will be described. As noted above, the
control panel 104 is located in a secure area remote from the
Wiegand reader 112. The reader 112 may receive its power from the
control panel 104 via the channel 204. The reader 112 is accessible
to a user attempting to obtain access to an asset, like the secure
area. In order to gain access, a user presents his/her credential
(e.g., smart card, RFID tag, magnetic stripe card, bar code card,
PDA, cellphone, or the like) to the reader 112. The information
received at the reader 112 is transmitted from the reader 112 to
the control panel 104 via the data channels 208 and/or 212. The
control panel 104 evaluates the information to determine whether
the credential is authorized to gain access to an asset associated
with reader 112. Depending upon the results of the evaluation, the
control panel 104 either performs a valid credential action (e.g.,
unlocks a door, unlocks a file, turns on a computer, opens a door,
etc.) or performs an invalid credential action (e.g., no action,
denies access, sounds an alarm, notifies security personnel, etc.)
Additionally the control panel 104 may send a signal to the reader
112 via the data channel 216 to flash a light on/off indicating to
the credential holder the results of the evaluation. The
communications protocol between the control panel 104 and the
reader 112 is typically considered unidirectional because most
often substantive data is sent from the reader 112 to the control
panel 104 and not from the control panel 104 to the reader 112.
[0050] Referring now to FIG. 3 a method of generating a signal for
transmission to an upstream device will be described in accordance
with at least some embodiments of the present invention. Initially,
the method begins when a credential, like an RFID device, is
presented to and read by a reader 112 (step 304). The reader 112
processes the received signal and determines what credential data
is contained therein (step 308). Examples of credential data
include, user name, social security number, title, access
permissions, key, password, manufacturer ID, site code, customer
code, and a unique ID. Once the credential data has been
determined, a rolling code is determined and generated by the code
generator 148 (step 312). A rolling code is generally selected from
a list of rolling codes. After a predetermined amount of time the
next rolling code from the list of rolling codes is selected by the
reader 112. Alternatively, an algorithm for generating a proper
code based upon certain criteria may be used. For example, a
choosing algorithm for a rolling code may be created based upon the
time of day, the number of credentials previously read at a given
reader 112, the number of messages transmitted from the reader to
the upstream device, a reader unique ID, reader manufacturer
identification number, etc. If the reader 112 sends the wrong
rolling code, then the control panel 104 will know something is
wrong with the reader 112. The reader 112 and control panel 104
generally have their copies of the rolling code (or rolling code
selection algorithms) synchronized upon installation. However, as
can be appreciated by one of skill in the art, the reader 112 and
control panel 104 may have their rolling codes synchronized based
upon other known methods.
[0051] Alternatively, a valid rolling code may be generated
arbitrarily, as long as the control panel 104 is in synchronization
with the reader 112 in determining what the next valid code is in a
rolling code sequence. For example, the reader 112 may use a
pseudo-random code generator and the control panel 104 may use an
exact copy of the generator. The system may be initiated such that
each generator determines, creates, and agrees upon the same valid
rolling code as each continues to operate properly. For example,
the reader 112 and the control panel 104 may use a previously
agreed upon sequence or list of valid rolling codes. The control
panel 104, at any random time, may change the order in which the
code generator 148 goes through the list. The control panel 104
could inform the reader 112 to change how it is working through the
list with a prompting signal send via an LED control signal, or may
do so through an interruption to the power supply of the reader
112. This ensures that the code generator 148 does not necessarily
have to go through a finite list of valid rolling codes in the same
order until a new list of codes is provided to the code generator
148. Rather, the same list may be used for a relatively longer
amount of time and a higher level of security can be
maintained.
[0052] In an alternative embodiment, data received from the
credential 116 may dictate what sequence the rolling code should
follow. For example, when a first type of credential 116 is read,
the reader 112 may use a first rolling code selection algorithm or
select a rolling code from a first list of rolling codes. When a
second type of credential 116 is read by the reader 112, the reader
may change to a different rolling code selection algorithm and/or
list of rolling codes. When the reader 112 switches from one
rolling code selection algorithm to another, it should indicate to
the upstream device that such a switch has been made.
Alternatively, the upstream device may recognize that a second type
of credential 116 has been read and automatically knows to switch
to a different rolling code selection algorithm.
[0053] Of course different algorithms may be used in a similar
fashion. The code generator 148 may use a first algorithm to
generate valid codes, then upon receiving a prompting signal from
an upstream device, like a control panel 104, a different algorithm
is used by the code generator 148. Furthermore, data used by the
algorithm to compute a valid rolling code may be changed in an
analogous way.
[0054] Once the rolling code data and credential data have been
determined, the reader 112 generates a message containing both the
credential data and rolling code data (step 316). In step 320, it
is determined if the signal containing the message is to be
encrypted. If the signal is not to be encrypted, then the reader
112 transmits the message (step 332). However, if the message is to
be encrypted, then an encryption key is determined (step 324).
Thereafter, the message is encrypted using the encryption key (step
328). By encrypting the message, the communications between the
reader 112 and the control panel 104 becomes more secure. Even if
someone is harvesting signals sent from the reader 112 to the
control panel 104, they must know the encryption/decryption key and
decrypt the message before any substantive information about the
message can be determined. Essentially, the encryption of the
message makes it more difficult for an attacker to steal a valid
rolling code and valid credential data.
[0055] In step 332, the message, whether encrypted or not, is
transmitted. Then, if the rolling code is based upon the number of
sent messages from a particular reader 112, the reader increments
to the next rolling code in the valid rolling code sequence (step
336). A valid rolling code may depend on the time of day or the
amount of time the reader 112 has been operational. In this case,
the rolling code is not necessarily updated after a message is
transmitted. In one embodiment, a list of valid rolling codes, for
example rolling codes A, B, C, D, and E may be used. The reader 112
starts by appending rolling code A to the first message it
generates and transmits to the control panel 104. The next rolling
code the reader 112 transmits may be rolling code B, then rolling
code C and so on. Once the reader 112 has went through the entire
list of rolling codes, it may start over by appending rolling code
A to the next message it generates. Alternatively, the reader may
append rolling code D after it has appended rolling code E and work
through the list of rolling codes that way. As long as the reader
112 follows the predetermined rolling code selection protocol, it
will continue to generate valid rolling codes. Using a list of a
select nunber of rolling codes provides for an inexpensive
implementation of the present invention. However, a persistent
attacker may eventually discover the finite list of rolling codes
thus jeopardizing the secure access system 100. In order to create
a more secure access system, valid rolling codes may be generated
based on predetermined algorithms using previously agreed upon
criteria.
[0056] As can be appreciated by one of skill in the art, the reader
112 is not the only device that may be used to generate a signal
containing both rolling code data and credential data. If there are
other devices present in an unsecured area, those devices may be
required to generate rolling code data in order to guarantee their
validity, and the validity of devices connected thereto to the
control panel 104. These devices may include credentials 116,
intermediate devices 120, and/or any other downstream device.
[0057] Referring now to FIG. 4, a method of receiving and
processing a signal containing credential and/or rolling code data
will be described in accordance with at least some embodiments of
the present invention. The method begins when a message is received
at an upstream device like a control panel 104 (step 404). The
control panel 104 determines if the message has been encrypted, or
should have been encrypted at step 408. If the message has been
encrypted, then the encryption key is determined (step 412). Using
the encryption key, the control panel 104 decrypts the message
(step 416). Once the message has been decrypted, or never was
encrypted, the reader 112 separates the credential data from the
rolling code data (step 420). It is not necessary to separate the
credential data from the rolling code data literally. As long as
the control panel 104 knows where the credential data ends and the
rolling code data starts.
[0058] Once the credential data has been separated from the rolling
code data, the control panel 104 compares the received rolling code
to the required code. The required code may be maintained at the
control panel 104 or in the database 144 separate from the control
panel 104. In step 428 it is determined if the received code
matches the required rolling code. If the received code does not
match the required code, then the control panel 104 determines that
a valid reader did not generate the signal or a valid reader has
been tampered with. In response to determining that there is a
problem with the reader 112, the control panel 104 performs invalid
reader logic (step 432). An invalid reader logic action may
include, sounding an alarm, notifying security/maintenance
personnel that a reader is defective, not opening a door, disabling
a reader by discontinuing power supply thereto, and other
appropriate actions associated with determining that a reader is
not valid and as are dictated by the particular circumstances.
However, if the reader 112 was valid and did generate a valid
rolling code, the credential data is analyzed in step 436. If the
credential data is determined to be invalid, then the control panel
104 performs invalid credential logic (step 440). An invalid
credential logic action may include actions similar to invalid
reader logic actions. Different actions may be taken by the control
panel 104 in response to determining that a credential is invalid
including, taking no action and/or controlling an LED on the reader
notifying the holder of the credential that access has not been
granted. However, if the control panel 104 can verify both the
rolling code data and credential data, then the control panel 104
performs valid message logic (step 444). A valid message logic
action may include opening/unlocking a door, unlocking a computer,
disabling an alarm, etc. Then if valid rolling codes are based on a
list of rolling codes, the control panel 104 increments to the next
valid code in the rolling code sequence (step 448). If the validity
of the reader 112 could not be determined in step 428 then the
control panel 104 typically does not increment to the next valid
code in the rolling code sequence. However, if the reader 112 was
valid, but the credential could not be authenticated, then a valid
reader 112 will expect to increment to the next code in the rolling
code sequence. Because of this, the control panel 104 should also
increment to the next code in the rolling code sequence so that the
valid reader 112 and control panel 104 continue to agree upon a
valid rolling code.
[0059] Referring now to FIG. 5, a method of continually sending an
update message from a unidirectional communications protocol device
to an upstream device will be described in accordance with at least
some embodiments of the present invention. Initially, the
downstream device, for example a reader 112, will determine an
initial code in the rolling code sequence (step 504). Then the
upstream device determines the periodicity with which it needs to
receive a valid code from a downstream device, for example a reader
112. Most of these determinations may be made upon installation of
the reader 112 or may be based upon other synchronization
techniques known in the art. A valid reader 112 is informed of the
required check in period and determines how often it needs to
transmit a valid code to the upstream device (step 508). The
downstream device waits until it is time to send an update signal
in step 512. If the required amount of time has not passed since
the last update message, the downstream device continues to wait at
step 512. Once it becomes time to transmit the message, the
downstream device generates and transmits a message to the upstream
device (step 516). The transmitted message contains the valid code
in the rolling code sequence. The valid code is sent to the
upstream device to verify to the upstream device that the
downstream device is still operational. Once the downstream device
has sent the message containing the valid rolling code, the
downstream device updates to the next code in the rolling code
sequence (step 520).
[0060] A downstream device may be required to send in an update
signal every second or fraction of a second for example. Having
such a short period between update signals may preclude an attacker
from cutting the connection between the upstream device and the
downstream device as any interruption in communication may be
discovered due to the high frequency of required updates. However,
in order to conserve bandwidth, a lower frequency of update may be
required.
[0061] As noted above a reader 112, intermediate device 120, hub
108, or control panel 104 may be considered an upstream and/or
downstream device depending on where it resides in relation to
other devices in the system. A first control panel 104 may be
connected to a master control panel. The first control panel 104
may be required to update its status to the master control panel in
which case the first control panel 104 would be considered the
downstream device and the master control panel would be considered
the upstream device.
[0062] Referring now to FIG. 6 a method of ensuring that a
downstream device is updated and valid will be described in
accordance with at least some embodiments of the present invention.
Initially, the period with which a downstream device is required to
"check-in" is determined (step 604). Then, the number of acceptable
missed messages or "check-ins" is determined (step 608). For a more
secure system, the number of acceptable missed messages may be set
to a very low number, i.e. zero, one, or two. In less secure
systems the number of acceptable missed messages may be set higher,
giving the system a higher tolerance to missed messages.
[0063] Once the required update rate and number of acceptable
missed messages is determined, a variable representing elapsed time
is set equal to zero (step 612). During this system initialization
a variable representing the number of missed messages is set equal
to zero (step 616). Then as time progresses the upstream device
waits to receive a signal from a downstream device. When the
predetermined amount of time between required updates has passed
(step 620), the upstream device determines if it has received a
valid rolling code (step 624). The upstream device may require the
downstream device to "check-in" right on the required time.
Alternatively, a downstream device may only be required to transmit
a valid code once every period. In the latter configuration, if a
downstream device sends a message in response to reading a
credential and appends a valid rolling code with that message, the
upstream device may not require another update message from the
downstream device during that time span. However, if the upstream
device does require the downstream device to transmit a valid
rolling code on the required time, even if the downstream device
already sent a message with a valid rolling code earlier in the
time period, the downstream device will be required to transmit
another valid rolling code at the predetermined time or in a
predetermined time window.
[0064] If the upstream device does receive a valid rolling code at
step 624 for that time period, then the method returns to step 612
and the variable representing elapsed time is set equal to zero. If
the upstream device does not receive a valid rolling code (e.g. no
check-in signal is received or the check-in signal included an
invalid rolling code), then the variable representing the number of
missed messages is incremented by one (step 628). In step 632, it
is determined if the number of missed check-in messages is greater
than the acceptable number of missed messages. If the threshold for
missed check-in messages has not been realized, then the method
returns to step 620 to wait for the next required check in time or
time window. If the threshold for missed check-in messages has been
exceeded then the upstream device determines that there is a
problem with the downstream device, typically a reader, and
performs the required steps to notify personnel that the subject
downstream device is malfunctioning (step 636).
[0065] Referring now to FIG. 7, a data structure employed by both
an upstream device and downstream device will be described in
accordance with at least some of the embodiments of the present
invention. The data structure may be in the form of a list of valid
rolling codes or a rolling code sequence 700. The rolling code
sequence 700 comprises a rolling code data field 704 and a required
check in time field 708. One copy of the rolling code sequence 700
is maintained in the upstream device that will be determining the
authenticity of a downstream device. The rolling code sequence 700
may alternatively be maintained in the database 144 and referenced
by the upstream device when analyzing a message that includes a
rolling code. In addition to maintaining the rolling code sequence
700 in the upstream device, the rolling code sequence 700 is
maintained in the downstream device. This ensures that both the
upstream and valid downstream device "agree" on a valid rolling
code. The rolling code sequence 700 may be employed in a system 100
that utilizes a unidirectional protocol because substantive data
typically cannot be sent from upstream device to the downstream
device. Therefore, each device in the system 100 can utilize the
rolling code sequence 700 to determine a valid rolling code without
engaging in bilateral communications. In the event that a
fraudulent reader not having the rolling code sequence 700 attempts
to send a message to the upstream device, the upstream device will
be able to determine that the downstream device is either
fraudulent or malfunctioning.
[0066] The rolling code sequence 700 may comprise up to x rolling
codes or rolling code generation variables that are required to be
transmitted at a check in time up to k periods after the first
check in time, where x and k are typically greater than one.
[0067] Each rolling code in the rolling code data field 704 may be
a unique predetermined rolling code. Alternatively, an algorithm
may use the data stored in the rolling code data field 704 in order
to generate a valid rolling code. The upstream device will expect
rolling code A from a downstream device at time T in order to
determine the authenticity of the downstream device. Then at a time
later than time T, the upstream device will expect rolling code B.
Since a valid downstream device will have the rolling code sequence
700, it will know what rolling code to send and when to send it. A
fraudulent reader on the other hand will not have access to the
rolling code sequence 700 and thus will not be able to send a valid
rolling code to the upstream device at the required time. This will
result in the upstream device determining that the downstream
device is not valid or is not functioning properly. A valid rolling
code generally includes the next rolling code to be sent in the
rolling code sequence. As can be appreciated, a less noise
sensitive system may be created that identifies more than one
rolling code as a valid rolling code. For example, an upstream
device may accept the next rolling code up to X more rolling codes
in the rolling code sequence. This valid rolling code buffer can be
implemented to provide some level of resistance to one or more
rolling codes being missed due to noise or other factors.
[0068] In an alternative configuration, a prompt signal may be sent
from the upstream device to the downstream device asking for the
next valid rolling code in the rolling code sequence 700. The
prompting signal may be sent via the LED control signal in the case
of the Wiegand protocol. When the prompt signal is received at the
downstream device, the next rolling code is chosen in the sequence
of rolling codes 700. This particular configuration is beneficial
in that a predetermined period of reply does not necessarily need
to be employed. Rather, a prompt signal may be sent randomly from
an upstream device to a downstream device. In order for the
downstream device to prove its authenticity to the upstream device,
it should generate a valid rolling code and transmit it back to the
upstream device.
[0069] As can be appreciated by one of skill in the art, the
relationship of an upstream device and a downstream device is
generally defined by the flow of credential information. The
downstream device transmits credential information to an upstream
device, which may further forward the information to another
upstream device or analyze the information to determine an
authenticity of the downstream device. Downstream devices are not
limited to a reader 112, but rather may include an intermediate
device 120, a credential 116, and/or a control panel 104. Moreover,
upstream devices are not limited to control panels 104, but also
may include a reader 112, an intermediate device 120, and/or a
credential 116.
[0070] The present invention, in various embodiments, includes
components, methods, processes, systems and/or apparatus
substantially as depicted and described herein, including various
embodiments, subcombinations, and subsets thereof. Those of skill
in the art will understand how to make and use the present
invention after understanding the present disclosure. The present
invention, in various embodiments, includes providing devices and
processes in the absence of items not depicted and/or described
herein or in various embodiments hereof, including in the absence
of such items as may have been used in previous devices or
processes, e.g., for improving performance, achieving ease and/or
reducing cost of implementation.
[0071] The foregoing discussion of the invention has been presented
for purposes of illustration and description. The foregoing is not
intended to limit the invention to the form or forms disclosed
herein. In the foregoing Detailed Description for example, various
features of the invention are grouped together in one or more
embodiments for the purpose of streamlining the disclosure. This
method of disclosure is not to be interpreted as reflecting an
intention that the claimed invention requires more features than
are expressly recited in each claim. Rather, as the following
claims reflect, inventive aspects lie in less than all features of
a single foregoing disclosed embodiment. Thus, the following claims
are hereby incorporated into this Detailed Description, with each
claim standing on its own as a separate preferred embodiment of the
invention.
[0072] Moreover though the description of the invention has
included description of one or more embodiments and certain
variations and modifications, other variations and modifications
are within the scope of the invention, e.g., as may be within the
skill and knowledge of those in the art, after understanding the
present disclosure. It is intended to obtain rights which include
alternative embodiments to the extent permitted, including
alternate, interchangeable and/or equivalent structures, functions,
ranges or steps to those claimed, whether or not such alternate,
interchangeable and/or equivalent structures, functions, ranges or
steps are disclosed herein, and without intending to publicly
dedicate any patentable subject matter.
* * * * *